In the crystalline lattice of minerals, the inter-atomic bonds are effective only over small distances, and can be broken if extended by a tensile stress. Stress concentration

The distribution of stress depends upon the mechanical properties of the individual minerals, but more importantly, upon the presence of cracks or flaws in the matrix, which act as sites for stress concentration. Crack propagation

Materials fail by crack propagation when the energy released by relaxing the strain energy is greater than the energy of the new surface produced. Modes of fracture

Breakage is achieved mainly by crushing, impact, and attrition. Therfore, there are three modes of fracture such as compressive, tensile, and shear fracture.

Lesson3 Primary Crushers (粗碎破碎机)

破碎在选矿中的作用:破碎属于矿石准备阶段，是矿物加工过程的重要环节，主要目的在于为后续磨矿或分选作业准备适宜的矿石粒度。

破碎机种类:按照作业性质分为粗碎、中碎和细碎三种；按照设备型式分为：颚式破碎机、旋回式破碎机、圆锥破碎机、辊式破碎机、冲击式破碎机等。 粗碎破碎机:主要包括颚式破碎机和旋回破碎机两大类.

颚式破碎机:破碎腔由固定颚板和运动颚板组成，通过动颚向对于定颚的摆动，使矿石受到挤压、破碎。根据动颚的运动特性，又分为简单摆动式和复杂摆动式两种。通常作为粗碎设备使用，不能挤满给矿。

旋回破碎机：破碎腔由固定锥（倒立截头圆锥）和固定锥中间的运动锥（正

立截头圆锥）组成，通过动锥向对于定锥的摆动，使矿石受到挤压、破碎。通常作为粗碎设备使用，其特点是允许挤满给矿、处理能力大。 颚式破碎机 结构示意图

颚式破碎机 原理示意图 简单摆动式（双肘板） 复杂摆动式（单肘板）

旋回破碎机 结构及原理